Jet servo-valves are well known. It is known that they are better at withstanding pollution of the fluid because the distance between the ejector and the deflector is greater than the distance between a nozzle and the flapper.
The pilot stage of a jet servo-valve has an ejector for ejecting a jet of fluid towards a receiver, such as deflector or an orifice. The ejector and the receiver are movable relative to each other. The relative movement between the receiver and the jet leaving the ejector enables the receiver to create pressure differences that are used for obtaining fine control over the movement of the spool of the distribution stage of the servo-valve.
Nevertheless, a known drawback of servo-valves with a jet pilot stage is the need to channel the fluid to the ejector by passing over the moving assembly of the servo-valve. Global standard SAE ARP490E requires servo-valves to be fastened and fed with hydraulic fluid via their bottom faces.